Research On Energy Absorption Of Pre-Folded Thin-Walled Structue Based On Additive Manufacturing

With the continuous development of high-speed trains in China,there is a constant increase in the demand for passive safety structures on trains.The primary goal of passive safety structure design is to absorb the energy generated during collisions in a controlled and efficient manner.Thin-walled structures have been widely used as energy absorption components on trains.However,as the performance requirements for energy absorption components continue to increase,there are higher demands placed on the design and manufacturing of thin-walled structures.In terms of design,traditional thin-walled structures cannot effectively utilize the material layout,which limits the energy absorption capacity of the structure.In terms of manufacturing,the precise manufacturing of thin-walled structures with complex topologies is difficult to achieve.To address these design and manufacturing issues,this paper proposes a graded optimization method based on uniform strain energy for pre-folded thin-walled tubes and pre-folded graded honeycomb structures.Selective laser melting technology was used to manufacture different pre-folded thin-walled structures,and their deformation patterns and energy absorption mechanisms are studied.The main research content and conclusions are as follows:(1)The influence of SLM process parameters and heat treatment on the mechanical properties of AlSi10 Mg thin-walled structures and the constitutive model of AlSi10 Mg material were investigated.Different combinations of process parameters were developed for printing schemes,and the influence of process parameters on defects was clarified through morphology analysis.The mechanism of regulating microstructure and mechanical properties by heat treatment was clarified by analyzing the grain size and microstructure of the thin-walled structures.Compression tests were conducted using a compression testing machine and a Hopkinson pressure bar system to obtain the stress-strain relationship of the material under different strain rates,and the constitutive model of AlSi10 Mg alloy was established.(2)A graded optimization method based on the uniform strain energy and the gradient thickness theory is proposed to optimize the pre-folded thin-walled tube with a diamond structure.A diamond structure was introduced onto the surface of a traditional thin-walled tube,creating a novel pre-folded thin-walled tube.The influence of the distribution and angle of the diamond structure on the energy absorption of the pre-folded structure under axial compression load was investigated through numerical simulation.The material distribution characteristics of the structure were changed by introducing the gradient thickness optimization design based on the principle of uniform strain energy.The axial crushing behavior of the gradient thickness pre-folded thin-walled tube was simulated using numerical simulation and compression experiments to validate the graded optimization method based on the uniform strain energy and analyze the mechanism by which the material distribution of the cross-section affects the energy absorption performance of the structure.(3)A novel graded honeycomb structure was designed based on biomimetic principles,and pre-folding structure and gradient thickness were introduced to further enhance the energy absorption performance of the structure.The effects of key geometric parameters such as unit cell ratio and number of folding cycles on the compressive performance of the structure were analyzed through numerical simulations and compression experiments to find the optimal combination of geometric parameters.Then,based on the minimum strain energy principle,the structure was partitioned according to the distribution of simulated plastic strain cloud under axial compression load,and the material thickness of each partition was optimized using a genetic algorithm to find the optimal combination that maximizes the energy absorption of the structure.The experimental results demonstrate that the pre-folded graded honeycomb structure not only enhances energy absorption efficiency,but also effectively reduces the initial peak load,in comparison to the traditional honeycomb structure.(4)The engineering application of graded honeycomb with pre-folded structure was realized in the train anti-climbing energy absorption device.The graded honeycomb with pre-folded structure and the optimized structure were respectively used as the core material to replace the traditional honeycomb filler in the anti-climbing device of a high-speed train.A high-speed train collision model was established,and the collision scenario of the train was simulated.Based on the EN15227 standard,eight-group train collision simulation analysis was conducted to obtain collision response data such as train energy dissipation,train speed,train hook interface force,and train acceleration.The research results show that under the application of the new anti-climbing device,the average deceleration,survival space compression,and wheel lift were all in compliance with the standard,and the collision performance was further improved compared to the traditional scheme.